<!DOCTYPE html>
<html>
<body>

<script>
// With deferral enabled we can get a lot of resource thrash when intermediate
// canvases and contexts are created, updated and drawn to a target canvas
// multiple times in a tight loop.
// See crbug.com/1030108

// We're more likely to see regressions with large canvases
const size = 1024;
var colourCounter = 0;

const targetCanvas = document.createElement("canvas");
targetCanvas.width = targetCanvas.height = size;
document.body.appendChild(targetCanvas);
const targetCtx = targetCanvas.getContext("2d");

const intermediateCanvas = document.createElement("canvas");
intermediateCanvas.width = intermediateCanvas.height = size;
const intermediateCtx = intermediateCanvas.getContext("2d");

function makeAndFillCanvasWithDifferentColor(i) {
  intermediateCtx.fillStyle = "rgba(0, 0, " + colourCounter + ", 1)";
  colourCounter = (colourCounter + 1) % 256;
  intermediateCtx.fillRect(0, 0, intermediateCanvas.width, intermediateCanvas.height);

  targetCtx.drawImage(intermediateCanvas, 0, 0);
}

function doRun() {
  // Make and fill many canvases
  for (let i = 0; i < 50; i++) {
    makeAndFillCanvasWithDifferentColor(i);
  }
  requestAnimationFrame(doRun);
}

window.onload = function () {
   doRun();
}

</script>
</body>
</html>
